Turbo coding is a powerful forward error correction (FEC) algorithm that achieves a coding gain close to the Shannon limit. Turbo encoders and turbo decoders have been adopted for use in the physical layers of a number of wireless standards, including WCDMA, CDMA2000, IEEE-802.16e (i.e., WiBro) and others. These standards operate at different data rates and implement turbo encoders and turbo decoders that are optimized for only one or two specific standards. Also, most conventional turbo encoders/decoders operate at relatively low data rates.
A software-defined radio (SDR) device uses reconfigurable hardware that may be programmed over-the-air to operate under different wireless standards. For example, an SDR transceiver in a wireless laptop computer or PDA may be configured by different software loads to operate in an IEEE-802.11x wireless network, a CDMA2000 wireless network, an OFDM/OFDMA wireless network, a GSM wireless network, or other types of networks. Many of these wireless standards require the use of turbo decoders.
However, conventional turbo decoders have significant drawbacks with respect to SDR applications. As noted above, conventional turbo decoders are optimized for decoding under only one or two specific standards. If an SDR device is required to support many wireless standards, more than one turbo decoder must be implemented in the SDR device. This leads to a complex transceiver design that makes inefficient use of chip space and has high power dissipation. Additionally, some of the newer wireless standards operate at relatively high data rates (e.g., WiBro, HSPDA, and the like). A turbo decoder that is optimized in terms of speed and power consumption for a low data rate standard is unlikely to be optimized in terms of speed and power consumption for a high data rate standard, and vice versa. Thus, conventional turbo decoder designs are not suitable for use in SDR applications.
Therefore, there is a need in the art for an improved reconfigurable turbo decoder for use in a software-defined radio (SDR) system.